ICM7212A Display Driver - Comprehensive Datasheet Summary

1. General Overview

ICM7212A is a four-digit, seven-segment LED display decoder/driver designed to drive non-multiplexed common-anode LED displays. It includes input data latches, BCD-to-segment decoders, and all necessary level translation and timing circuits.

Key Features:

• Directly drives four-digit, 7-segment common-anode LED displays
• No external components required
• Low power CMOS technology
• Code B output character font (suffix "A" indicates Code B font)
• Available in two interface versions: Multiplexed BCD and Microprocessor (μP) interface
• Reduces system cost by eliminating external level translators, segment drivers, and current-limiting resistors
• 28 open-drain constant-current outputs (8mA typical per segment)

2. Device Nomenclature and Ordering Information

Device Types:

• ICM7212: Hexadecimal output font
• ICM7212A: Code B output font
• ICM7212M: Microprocessor interface, hexadecimal font
• ICM7212AM: Microprocessor interface, Code B font

Part Numbers and Packages:

3. Pin Configurations

40-Lead DIP (Multiplexed BCD Version):

40-Lead DIP (Microprocessor Interface Version - M Suffix):

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44-Lead Chip Carrier (Q Package):

• Same functionality as DIP but in surface-mount Quad Pack configuration

4. Electrical Characteristics

Absolute Maximum Ratings:

• Supply Voltage: 6.5V
• Input Voltage: V+ + 0.3V to GND - 0.3V
• Power Dissipation: 0.5W @ 70°C (package limit)
• Operating Temperature: -20°C to +85°C
• Storage Temperature: -55°C to +125°C

Operating Characteristics (V+ = 5V, TA = 25°C):

ICM7212A (Common Anode LED):

5. Functional Description

5.1 Digital Interface Options

A. Multiplexed BCD Interface

• 8 input lines: 4 BCD data lines (D1-D4, B0-B3) + 4 digit strobes (DIGIT SELECT D4-D1)
• Operation: When a digit strobe goes high, an internal pulse latches decoded data into the 7-bit latch for that digit
• Data Setup Time: -100 ns (negative setup time allows strobe before data valid)
• Data Hold Time: 200 ns minimum
• Truth Table:Strobe high → Latch data for that digitStrobe low → Data held constant, no updates

B. Microprocessor Interface (M Suffix)

• 8 input lines: 4 BCD data lines + 2 digit address lines (DS1, DS2) + 2 active-low chip selects (CS1, CS2)
• Operation: Data written when both CS lines are low; internal one-shot transfers data to digit latch
• Accessed as: 4 "write-only" memory locations
• Chip Select Pulse Width: 200 ns minimum
• Data Setup/Hold: 100 ns setup, 10 ns hold

5.2 Character Font (Code B - ICM7212A)

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6. Timing Characteristics

Multiplexed Input Configuration:

• Digit Select Active Pulse Width: 1 μs minimum
• Inter-Digit Select Time: 2 μs minimum

Microprocessor Interface:

• Chip Select Active Pulse Width: 200 ns
• Inter-Chip Select Time: 2 μs
• Data Ready Pulse: Automatic one-shot generation

7. Application Information

7.1 Brightness Control

Two methods for LED brightness adjustment:

Method 1: Voltage Control

• BRT pin (pin 5) voltage controls segment current
• Use 100kΩ to 1MΩ potentiometer
• Can be combined with photoresistor for automatic ambient light adjustment
• Method 2: Duty Cycle Modulation
• Pulse BRT pin between "full on" and "blanked" states
• Can use ICM7555 timer or similar circuit
• Allows PWM-based brightness control

7.2 Power Dissipation Management

Maximum power dissipation must not exceed 500mW @ 70°C.

Example Calculation (Display "8888"):

• Power = 28 segments × 8mA × (5V - 1.6V) = 760mW (EXCEEDS LIMIT)
• Solutions:

1. Reduce LED current: Use brightness control
2. Reduce voltage across drivers:Lower system V+ supplyAdd series diodes (2 diodes reduce power by ~35%)

7.3 Display Blanking

• BRT pin at V+ → Full brightness
• BRT pin at GND → Display blanked (all segments off)

8. Typical Application Circuits

8.1 Basic 4-Digit LED Display

+5V → V+ (Pin 1)
BRT (Pin 5) → Brightness control potentiometer
Data inputs → Microcontroller BCD outputs
Digit strobes → Microcontroller select lines
28 segment outputs → LED display segments
GND → Ground pins

8.2 Microprocessor Interface Example (8048)

• Use MOVX instructions to address external RAM locations
• 74LS138 decoder generates CS signals for 8 blocks of 4 bytes each
• Starting address: 32 decimal

8.3 Reducing Power Dissipation

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+5V → V+ (Pin 1)
BRT (Pin 5) → Brightness control
LED Display Anodes → +5V through 2× 1N4001 diodes
Segment outputs → LED segments
This reduces voltage across drivers from 3.4V to 2.2V

9. Physical Characteristics

Package Details:

• 40-Lead Plastic DIP (PL):Dimensions: 0.600" - 0.620" width, 2.086" lengthThermal Resistance: θJA = 10°C/W, θJC = 45°C/W
• 44-Lead Chip Carrier (Q):Quad Pack surface mount package0.050" lead spacing

ESD Protection:

• All pins except pin 29: >2000V (MIL-STD-883B)
• Pin 29: 1500V (due to special test functions)

10. Design Considerations

Important Notes:

1. Power Sequencing: In multi-supply systems, power ICM7212 first before applying signals from external sources
2. Latch-up Prevention: Do not apply voltages >V+ or <GND to any terminal due to SCR structure in CMOS process
3. Unused Segments: Should be tied to ground, not left floating
4. Grounding: Use both ground pins for high current applications to minimize IR drops
5. Thermal Management: Monitor power dissipation especially when driving all segments at high ambient temperatures

11. Related Products

• ICM7211: LCD display driver version (non-multiplexed)
• ICM7217: 4-digit LED decoder with multiplexed output capability
• ICL7135: 4½ digit A/D converter (can interface with ICM7212A)